The present invention relates to a filter for use with x-ray examining devices. In particular, the invention is a filter which is used to improve the quality of x-ray images of the cervical-thoracic region of the spine in a lateral projection.
X-ray imaging is an important diagnostic tool which is used by medical professionals on a daily basis. An x-ray system has several fundamental components: a source of an ionizing or penetrative radiation (normally an x-ray tube), and object plane in which the object (typically a patient) is positioned, an image plane on the opposite side of the object plane from the radiation source, and an image recording medium or device disposed at the image plane. The image recording medium may be an x-ray sensitive film, a fluorescent display screen, or an electronic image amplifier.
One of the many uses of x-ray examination is in an emergency room to determine the nature and extent of trauma in accident cases. For example, a patient may be wheeled into the emergency room with a neck collar which has been applied because of a suspected cervical injury. The cervical/thoracic region of the spine should be properly visualized before moving the patient. In the past, the images of the cervical/thoracic region have been of poor quality because of the difference in thickness and mass of the cervical and thoracic regions.
In order to obtain a proper exposure of the thoracic spine, a relatively high level of x-ray exposure (similar to a lateral lumbar spine exposure) is required because in the lateral projection the thoracic spine has both high tissue and bone density. This high level of exposure greatly exceeds the exposure levels needed to image the cervical spine. As a result, an x-ray image of the cervical/thoracic region will either show the thoracic spine region while the cervical spine region is significantly overexposed, or show the cervical spine region with the thoracic spine region significantly underexposed.
Typically, a physician examining x-ray images of a patient with suspected cervical injury will attempt to count the cervical vertebrae in order to locate the seventh cervical vertebra and the first thoracic vertebra. It is important to determine whether the seventh cervical and first thoracic vertebrae are aligned before moving a patient in order to avoid causing permanent spinal cord injuries.
There is a need for a improved x-ray system in which the cervical and upper thoracic spine regions can be imaged in a single x-ray image with acceptable levels of x-ray exposure in both the cervical and thoracic spine regions.